...in my opinion.
The rump rope is good, but a bit of a hassle.
Positioning next to the horse shoulder is good. For example, I steer Nicky around by lining up my leg with his front leg, and then I just lay a hand on his neck to steer him around.
The stock crop to tap at the rump has never worked out for me; our horses are too short. I get the idea that you hold it in the same hand and then tap their bottom to get them to go forward, but they're (crops/whips) all the wrong length for minis.
I'm surprised nobody mentioned pressure/release. I read a really good web-site that helped me out hugely with that. I wouldn't post the link, though, because this guy has peeved off 99.9 percent of the women on the internet.
I think, to have them lead consistently, you have to make them want to walk with you. One of the easiest for me is bribes. A little smidge of a carrot treat goes a long way towards walking on the lead. (shrinking and hiding, but hey, it works for me.)